The present invention relates to a novel atmospheric oxygen element and assembly thereof with characteristics as disclosed by German Auslegeschrift No. 2,331,739, the entire disclosure of which is incorporated herein by reference as is the priority document referenced in my attached declaration. Such atmospheric oxygen elements have a negative electrode preferably of zinc and an electrolyte of manganese (II) chloride. The positive, active electrode mass, also called the depoolarizer mass, comprises, for example, activated charcoal with admixtures.
The carrier foil of the known atmospheric oxygen element is conventionally folded around a piece of cardboard stamped out in the shape of a comb so that a unilaterally open pocket is formed into which air may penetrate. The electrode mass pressed into conventional electrode plates is positioned on the exterior of the carrier foil. The part of the carrier foil covered by the electrode plates has punched holes so that air may penetrate into the positive electrode plates from the open pocket through the carrier foil. Thus, air always penetrates from the open pocket through the carrier foil into a broad side of the electrode plates according to conventional elements.
For a secure holding of the electrode plates on the carrier foil, the arrangement of carrier foil and electrodes is then dipped into a stiffening varnish, for example, cellulose triacetate varnish, to a depth deep enough so that not only the electrode plates themselves, but a part of the carrier foils projecting above the electrode plates are coated by the lacquer.
Atmospheric oxygen elements with manganese chloride as an electrolyte have a very high specific capacity (Ah/cm.sup.3) and an excellent storage life. Smaller elements, however, have too low a current carrying capacity. As a result of the present invention, the carrying capacity is increased such that elements of the size of monocells may deliver about 200 mA, thereby replacing monocells. In order to achieve this, the present invention reduces the thickness of the plate-shaped elements considerably, so that it will be possible to accommodate more positive and negative electrode surfaces in a given container.
Surprisingly, a current carrying capacity of 2 mA/cm.sup.2 cathode surface, as is customary with conventional plate elements, may be achieved according to the present invention with considerably smaller thicknesses of the positive electrode mass layer.
According to the present invention, a carrier foil which has a conductive foil on either side is provided on both sides with a positive electrode plate. The positive electrode mass of the present invention is applied particularly loosely so that a supply of atmospheric oxygen from the front of the element is sufficient.
The supply of atmospheric oxygen according to the present invention is accomplished by utilizing a front cover plate having air feeders. Thus, according to the present invention, the stiffening varnish is kept free of the air feeders during the customary dipping process, and, additionally, the electrolyte is prevented from penetrating into the interior portions of the positive electrode through the air feeders. Moreover, the stiffening varnish adheres safely to the cover plate so that any curving of the electrode plates under the influence of the stiffening varnish contracting and breaking loose from the carrier foil during drying is prevented. In order to achieve the above simultaneously, the air feeders are protected by lateral upwardly extending walls which protect the air feeders from the varnish yet allows support of the cover and electrode plates.
The individual positive electrodes according to the present invention may be placed in a container in larger numbers, when compared to conventional assemblies by alternating with negative electrodes. As a result, a higher overall current carrying capacity may be achieved.
The lateral walls provided according to the present invention, which surround and protect the air feeders of the cover plate, may surround the cover plate as a whole or particular groupings of the air feeders. Alternately, individual wall members may be provided to individually protect each air feeder.
The positive electrode mass must be applied to the carrier foil in a loose manner due to the frontal aeration. Therefore, difficulties may arise for holding the electrode mass firmly on both sides of the carrier foil until the stiffening lacquer dipping process is concluded. The surfaces of the carrier foil may be treated chemically in a suitable manner to achieve better adhesion of the electrode mass. Under certain circumstances, it will be sufficient to provide the carrier foil with apertures, so that the electrode masses applied on both sides will bond together. These apertures therefore, contrary to the status of the prior devices, are not required for aeration, although they may make an air exchange between two electrode plates possible.
An additional mechanical protection may be given to the narrow sides of the element left open by the cover plate by utilizing a U-shaped strip.
A single element has particular significance, whenever it is desired to accommodate it in a very flat space. The capacity of such elements may be increased by a parallel connection which conventionally could be achieved in a cumbersome and expensive manner by welding the individual elements together. According to the present invention, however, a parallel connection of several individual elements may be produced without welding or similar processes. Since the individual elements are very thin, an element of greater capacity will be obtained according to this invention in a given space when compared to conventional positive electrode plates.
According to an embodiment of this invention, a continuous carrier foil may be provided with individual positive electrode plates on both sides and may then be rectangularly folded forming a generally square wave shape. The negative electrode is folded in a like manner so that a portion of the negative electrode sheet metal lies between two adjacent positive electrode plates. In this manner, a number of positive and negative electrode plates may be connected in parallel arrangement without the necessity of welding points. An atmospheric oxygen element of this kind does, therefore, not only have a high current carrying capacity but it may also be manufactured at a relatively low cost. It is also possible according to this embodiment to avoid short circuits and secure against longitudinal shifting by a simple spatial arangement of the two interlocking square wave shapes of both electrodes.